SENSORIMOTOR CORTICAL ACTIVITIES 



803 



SENSORY SEQUENCE 



Po Uc«ntf»l , _« ^ 



Prtcentrftl 



MOTOR sequence: 



TOES 



FOOT 



LtC(HIPTBn»TJ 



mP 



TRUNK 



StIOULKR 



AUn 



ELBOW 



roREAKn 



WRIST 

 ■KANO 



srTALL nwcEH 



RING riNCcn 



mOOLE PNUR 



INDEX FINUR 



THUnB 



EYE 



NOSE 



FACE 



LIPS 



TONX/E 



TASTT 



JAW A^« TXtTH 



THROAT 



FIG. 4. Motor and sensory sequences in human pre- and postcentral gyrus. This scheme of repre- 

 sentation does not take into account the considerable overlap of body parts depicted in figure 3. 

 [From Penfield & Boldrey (356).] 



rump length of 33 mm, forelimb movements followed 

 cortical stimulation, but other body regions remained 

 unresponsive. In these animals birth occurs after a 

 lo-day gestation period, and the immaturely born 

 young (crown-rump length, 1 1 mm) crawls to the 

 pouch, using the forelimbs and swaying the head as 

 far as possible to the opposite side to the propelling 

 hand (189). Movements of the face appear next but 

 cannot be obtained by stimulation until the 76th day. 

 Huber suggests that precedence in structural devel- 

 opment and early use of the forelimbs arises here in 

 connection with the neonatal processes peculiar to 

 the marsupial and not as part of a phylogenetic de- 

 \elopmental sequence (212). No hind-limb move- 

 ments were seen by these observers from cortical 

 stimulation of any stage of the pouch-young opossum 

 nor from a larger series of adult opossums. 



In the placental mammals, newborn and very 

 young specimens of cats, dogs, rabbits and guinea 

 pigs have been studied. Most of these studies are to be 

 found in the older literature which has been reviewed 

 by Huber (212). Stimulation has yielded varying 

 results (120, 247, 249, 311, 316-318, 348, 349, 407, 

 443, 470). Mills (318) found that for several days 

 after birth the cortex of the cat was unresponsive to 

 electrical stimulation under ether anesthesia, but 

 that in some cases it was functionally active before 

 the eyes opened, about the gth day. Centers for the 



forelimbs responded earlier than those for the hind 

 limbs, and head movements appeared at a later date 

 than movements of the limbs. In similar experiments 

 in newborn kittens (249) forelimb movements were 

 seen, however, but movements of the hind limbs were 

 not obtained until the i6th day, and facial move- 

 ments at 21 days. Soltmann (407) observed a similar 

 sequence in dogs under ether, chloroform and mor- 

 phine. In large dogs, cortical motor centers may be- 

 come functionally active at a later date tlian in small 

 breeds, such as terriers (212). 



CORTICAL STIMULATION STUDIES OF 

 ROLANDIC MOTOR AREA 



The selection of the optimal parameters of electric 

 stimulating currents has long exercised the interest of 

 physiologists. VVyss & Obrador (483) emphasized the 

 relation between the pulse duration of the stimulating 

 current and the threshold for various types of move- 

 ments produced by cortical stimulation. Frequency, 

 wave form and pulse duration are all intimately in- 

 voked, apart from such additional variables as elec- 

 trode configuration and spacing, and type and depth 

 of anesthesia. These problems have been studied par- 

 ticularly with respect to the responses elicited from 

 the Rolandic area. As indicated in the maps of 



